1. Field of the Invention
The present invention relates to an object detecting apparatus for detecting an object by transmitting electromagnetic waves such as laser beams or millimeter waves to the object and receiving reflected waves due to reflection of the electromagnetic waves from the object.
2. Description of the Related Art
For example, Unexamined Japanese Patent Publication (kokai) No. Hei. 8-240660 discloses an object detecting apparatus for detecting an object serving as an obstacle by receiving a reflected wave due to reflection of an electromagnetic wave such as a laser beam or the like transmitted ahead in a direction of movement of a vehicle. The apparatus thereby generates an alarm or performs an avoidance motion automatically in order to avoid a collision with the object.
Such an object detecting apparatus is intended to detect an obstacle such as a vehicle running in front or the like existing on a course of its own vehicle. Consequently, it is undesirable that a pedestrian bridge, a land bridge, a traffic sign, cat's eyes, or the like, which would not be an obstacle, is detected as an obstacle by mistake. Therefore, the vertical width between upper and lower limits of a detection region to which an electromagnetic wave is transmitted may be preferably set to be narrow and the detection region may be preferably disposed to be substantially parallel with the road. If the vertical width between upper and lower limits of the detection region is set to be narrow, however, there is a possibility that a pedestrian bridge, a land bridge, a traffic sign, cat's eyes, or the like, is detected by mistake because an original obstacle such as a vehicle running in front, or the like, cannot be detected when the vertical angle of the detection region changes in accordance with main factors such as accuracy in attachment of the object detecting apparatus to a vehicle body, nose up caused by sudden acceleration, nose dive caused by sudden braking, undulation of the road surface, loading condition, etc.